In a battery system having a plurality of battery cells, the battery cells are thermally connected to one another via coupling layers. The battery cells which are described below are secondary battery cells, i.e. accumulator cells. For the safe operation of such battery systems the temperature of the individual battery cells is monitored. For this purpose, it is desirable to determine the temperature of the individual battery cells as accurately as possible. Owing to uneven temperature distribution, the temperature of individual battery cells in the battery system cannot be detected reliably for all the battery cells by means of a single temperature sensor. Unequal temperature distribution occurs not only at the module level but also at the cell level. Therefore, it is not possible to use conventional methods to determine the actual core temperature of the battery cell.
EP 3 015 835 A1, which is incorporated by reference herein, discloses a method for estimating the temperature of a battery cell, wherein the relationship between the internal resistance, the state of charge, the aging and the temperature of the battery cell is produced by means of a reference model of the battery cell. The temperature of the battery cell is determined by determining the actual internal resistance, by estimating the actual state of charge and by estimating the aging of the battery cell.
DE 10 2011 116 779 A1, which is incorporated by reference herein, describes a method for the sensortess estimation of the core temperature of a battery cell, wherein a core temperature of the battery cell is estimated by determining an internal resistance of the battery cell and by means of a function of the transmission of thermal energy of the battery cell.